Alloy for electrical conductors



Q also inclu Patented Aug. .6, 1929.

UNITED STATES? PATENT OFFICE.

MICHAEL enonen xoasunsxr, now BY rumour calmer: or name uremia GEORGE CORSON, or :rncxson HEIGHTS, NEW YORK, essmnon 'ro nnnc'rno 1mm;- nuneroan comrm, A conronn'rron or wnsr vimmm I Armor For, uncommon. connucrona- No Drawing.

probably the most effective addition to copper for increasing its tensile strength, Thus copper has a tensile strength of only about 35,000 pounds persquare inch when annealed and only 54,000 to 56,000 pounds when hard-drawn, while a copper-chromium alloy containing a small percentage of chromium pounds as cold-rolled from the cast ingot. The conductivit of the copper-chromium 2 alloy as cold r01 ed from the ingot however, is only about Matthiesen standard, and itis therefore not comparable WltlLCOP- per as a material for electrical conductors. If'the cold-rolled alloy is heated for a so sufficient time at usual annealing temperatures its conductivity is considerably improved \but the annealed alloy has a tensile strength but little higher than that of annealedpure copper, so that it has no advan- 35 tage over copper as a material for conductors.

The invention is a process whereby the conductivity of a strong c'opper'alloy, such as a copperchromium'allo may be made. 0 much higher than that exhi ited by the cast alloy, without seriously impairing the tensile stren th of the alloy. The invention des the product of this process and more particularlyit' includes alloys, for ex- 15" ample copper-chromium alloys, having a conductivity in excess of M. -S., and a tensile strength in excess of 70,000 pounds per'squarei'nch when in the form of wire of one-fourth inch diameter'.'

The process of the invention consists in annealing thexalloy and so limiting the time and'temperature of that the above lar material. has a tensile strength of 72,000 to 80,000

Application filed December 9, 1921. Serial No. 754,857.

mentioned result is attained. Tem ratures as low as 400. C. may be used,

hours to ing about the maximum increase in conductivity. Higher annealing temperatures make it possible greatly to reduce the annealing period, and indeed this period must be curtailed or the high tensile strength characteristic of the cast alloy will be in a large measure lost. At about700 0., the desired change in the alloy can be brought about in as little as five minutes in' some cases. The above examples illustrating the inverse relation between time and'temperature and the preferred tem erature range will enable those skilled in t e art .to practise the invention, The times will vary somewhat with the composition of the alloy, but a few easily performed tests will sufioe tofix the optimum conditions'for a particu- My preferred alloy is copper containing 0.5% to 3.0% chromium. As the chromium content is increased within the ran e indi-q ut; with n t such temperatures it requires two or three cated, the tensile stren th of the al oy will I increase, but the rate 0 increase falls ofi' so that it will usually be uneconomical to use more than 3% of chromium. v

Y I prefer also to incorporate into. the alloy v much higher percentages of'the deoxidizer may be used. This not only obviates manuand sounder, metals to be made. I prefer to add the deoxidizer in amount between 0.03% and 0.3%. phosphorus gives good results. Unless sufli -facturing difliculties but it permits cleaner About 0.2% of silicon or cient deoxidiz'en is present to reduce any J cuprous oxid present, this will be reduced by porate the deoxidizer in any usual or suitable way, the quantity added being generally not more than 0.3%. Under certain conditions considerably more than 0.3% of the deoxidizer may remain in the alloy without seriously decreasing its conductivity. Before the chromium is added, the temperature of the copper is raised to expedite alloying'. A temperature 'of about 1275 C. gives results, and it is usually, undesirable to exceed 1350 C. since high temperatures promote oxidation of the chromium d too small nor too large, since 'on the one hand too much oxidation takes place and on the other the alloying takes place too slowly. Pea-sized lumps of chromium are suitable. The bath should be stirred vigor-- ously while the chromium is dissolving. The foregoingis a' preferred method of provducing the alloy, but variations, such for example as addin the chromiugn as a preformed copper-chromium or other alloy, are permissible.

The. metal may be cast and the ingots alloying. The chromium should be added in pieces which are neither more or less reduced in cross-section before annealing them in accordance with the invention, but the final drawing should follow the annealing in order that the finished wire or the like may have the high strength which is characteristic of hard-drawn material. Alloys have been prepared in accordance with the invention which exhibit a conductivity of 80% coupled with a tensile strength of 72,000 to 80,000 pounds per square inch.

I claim:

1. Process of treating analloy containing 0.5% to 3.0% chromium with the balance substantially copper which comprises subjecting the alloy when it has substantially the tensile strength of the cast and harddrawn material to a heat-treatment equivalent to annealing for two to three hours at 400 C., and then hard-drawing the annealed alloy into wire.

2. Process of treating an alloy containing 0.5% to 3.0% of chromium with the balance substantially copper which comprises sub- 'jecting such alloy, in a condition wherein it has a high tensile-strength, to an annealing operation in the temperature ran e 400 C. to 700 C. and of such regulate duration that the conductivity of the cold alloy is increased to at least 75% M. S. and the tensile strength is not reduced below 70,000

pounds per square inch.

In testimony whereof, I aflix my signature.

MICHAEL GEORGE KORSUNSKY. 

